A light organ (aka color
organ) is a device that uses sound to trigger light. More
sophisticated versions of this concept can be found at any club with a
dj and lighting rig. In fact, rather than sound effects, these
devices were primarily designed to trigger multi-colored lights by
whatever music you put on. Often these were simple enclosures of
lights you put on top of your stereo or on the wall next to your
blacklight posters, man.
In spite of its arty origins, all I've really ever wanted to do with a
circuit like this is to have it trigger lightning to a thunderous
Selecting a light organ
There are several options to consider when purchasing a light organ:
Trigger method - Can be via:
- built-in microphone, but the
disadvantage is that the lights will also be triggered by background
noise in the vicinity.
- speaker output. You connect it
to the same place as your speakers
connect. This is really easy if you have a stereo that simply
onto bare wires. It's a little more complicated if you're using
jacks or similar.
- line input. This is probably
the easiest since all you need is a
splitter, then connect your mp3 player to the stereo with one line and
to the light organ with the other.
Channels - The simplest light organs
only have one output. You can
connect several lights to this, of course, but a multi-channel organ
will usually trigger separate lights based on the different
frequencies. The idea is that the bass frequencies trigger, say,
blue light while the mids do the greens, and the treble range does the
reds (or whatever). Three channels is adequate for lightning, but
can find circuits with up to seven channels.
How much power the can circuit handle. Odds are your
application will be something in your home or front yard rather than an
arena, but you need the device to be commensurate with the demands you
expect to put on it.
numerous kits available to build your own light organ or you
can buy one already assembled at fairly steep prices (i.e., upwards of
a hundred vs. a kit that costs less than $20). I purchased mine
the project box I put it in) through Electronic Goldmine. Here's
a link right to the
It took maybe an hour or so to build,
probably less if I would have had
my soldering iron set out with a convenient place to work at the
Maybe two hours total if you count cutting holes in the project box as
well at the testing.
The only problem I had with it was that I
connected the power cord
backwards (i.e., it's a polarized plug), so it didn't work until I
realized the flaw and reversed it.
This model has a sensitivity control to
get the lights to trigger at
just the output you want. This is really great for lightning
want the lights to be flickering a lot, meaning the input is rocking on
a knife-edge trigger, pulsing back and forth when the trigger voltage
is near its peak.
Some circuits also have control over the
frequencies, which is a nice luxury, but I could see someone ending up
spending entirely too much time tweaking the effects to go with their
If you are good with assembling your own
circuits, there are dozens of
schematics around the web with any number of options. This is not
terribly complicated device, so you can design your own with the best
features of the examples available.
"soundtrack." The numbers at the front of the file names are
ostensibly track numbers, but I intentionally went through and wrote
this like line numbers in BASIC code (for those children of the '80s
who remember this practice). Note how the sound effects are all
lines. I just inserted mp3s of silence between those.
just a few seconds of silence, other times it's four minutes. The
is not to over-do the thunder but rather to wait until another group of
Trick or Treaters is on the front porch before the lightning strikes
again. I even threw in a couple lightning strikes almost back to
just to mess with the kids.
15 Silence - 1 minute.mp3
20 Thunder crash 2.mp3
25 Silence - 3 minutes.mp3
30 Thunder crash 3.mp3
35 Silence - 2 minutes.mp3
37 Silence - 2 minutes.mp3
40 Thunder crash 4.mp3
45 Silence - 1 minute.mp3
50 Thunder crash 5.mp3
55 Silence - 3 minutes.mp3
60 Thunder crash 6.mp3
65 Silence - 2 minutes.mp3
70 Lightning strike with thunder crash
75 Silence - 3 minutes.mp3
80 Lightning strike with thunder crash
85 Silence - 2 minutes.mp3
90 Simulated lightning strike (left to
95 Silence - 2sec.mp3
97 Simulated lightning strike (right to
99 Silence - 3 minutes.mp3
Another option is to have just randomize
the sounds and silence by putting the player on "shuffle."
However, you can sometimes end up with periods of endless thunder or
long gaps without and sounds. I just didn't want to leave things
similarly devise a soundtrack with alternate spaces of silence to
trigger something like:
- Flashing lights to accompany
electrical noises and screams from an electric chair.
- Have prop ghosts come to life
triggered by the soundtrack.
- Eyes hidden in the bushes or trees
around your house.
Also, it's possible to use audio to drive a
servo to make animatronics talk by moving the jaw. There are some
tutorials around the web on how to do that, especially with skulls.
Random idea: A circuit driven by speaker
voltage could theoretically be
used as a two-channel device by simply taking advantage of the fact the
audio can be edited in stereo (i.e., pan some sounds hard left/right to
trigger only one controller or the other).
2011, 2012 the Ale[x]orcist.